The victim's mother told police the teenagers threatened and demeaned her child, who was the victim of a violent crime allegedly at the hands of a friend of the suspects.
The mother said the teens repeatedly harassed her child "physically and through social media."
The seven teenagers were charged with felony witness intimidation after police said they found evidence of harassment on Twitter and Facebook, the Boston Globe reported Saturday.
"Nobody came after this person with a knife or a gun in their hand, but you take it for what it is, and it was harassment. It was threatening. The intimidation factor was there. Threats and comments were made that were upsetting to the victim," Grafton Police Chief Normand Crepeau Jr. said.
Among those arrested were Joseph Todisco, 18, Anthony Masterson, 19, and Daniel Guzetti, 19. The names of four others were withheld because they were juveniles. A 17-year-old boy faced an additional charge of criminal harassment, and a second 17-year-old faced additional charges of criminal harassment and threatening to commit a crime, the Globe said. The other two juveniles were 14 and 15 years old.
"The Grafton Public Schools takes bullying and harassment very seriously," Grafton High School Principal James Pignataro said in an email Saturday. "Currently this is being treated as a police matter. We are limited in what we can say at this time but can assure you that we will continue to work closely with the police and will take further school-based actions as needed."